Effects of an alien vertebrate herbivore on the regeneration of endangered vegetation communities: Example of feral rusa deer impacts on the restoration of subtropical rainforest on an abandoned mine site in the Illawarra region.
School of Earth & Environmental Sciences
Nilar, M H M, Effects of an alien vertebrate herbivore on the regeneration of endangered vegetation communities: Example of feral rusa deer impacts on the restoration of subtropical rainforest on an abandoned mine site in the Illawarra region., BEnviSci Hons, School of Earth & Environmental Sciences, University of Wollongong, 2017.
Anthropogenic land clearance is responsible for reductions in the extent of native vegetation and losses in biodiversity, however restoration ecology could reverse this damage. The Illawarra Subtropical Rainforest is an endangered ecological community currently undergoing restoration, but is threatened by alien plant species and an introduced herbivore Cervus timorensis.
This honours project examined the effects of vertebrate herbivores on the establishment of re-vegetated tree and shrub seedlings, and the composition of regenerating Illawarra Subtropical Rainforest. The study was performed on the deforested slopes of an abandoned coal mine on the foothills of the Illawarra Escarpment, whereby local land managers and restoration practitioners used a combination of alien plant control, followed by planting of nursery-grown native tree and shrub seedlings and herbivore exclusion with fenced plots to encourage natural regeneration.
Five key questions were addressed by this honours project: (1) how widespread is browsing damage to revegetated shrub and tree seedlings, and does such damage limit plant establishment? (2) Is there a difference in effectiveness of different guard types (fenced plots versus individual wire or corflute guards) at protecting seedlings from browsing damage? (3) Do plant species differ in their susceptibility to attack by vertebrate browsers? (4) What are the patterns of vertebrate herbivore diversity and activity across the revegetated habitat versus established patches of forest?
Plant responses to browsing were assessed by measuring proportion of stems and apical shoots that were damaged by herbivores for 900 nursery-grown and revegetated rainforest shrub and tree seedlings (54 species) in four different protective treatments: fenced plots, individual wire and corflute guards and unprotected control plants. Vegetation community responses to herbivores were assessed by comparing composition and vegetation structure between fenced and adjacent unfenced control plots. Vertebrate identity and activity were assessed with camera traps deployed across three habitats: deforested grassy areas, deforested areas that had been revegetated and establish patches of mature rainforest.
Unprotected seedlings generally experienced significantly higher (more than 40%) vertebrate herbivore damage, but varied among species and protective guard type. Corflute guards were less effective than individual wire guards or fenced plots at protecting seedlings from browsing damage. Fenced plots were most effective at protective seedlings from damage but also had the benefit of enhancing the diversity and abundance of non-planted species and the foliage cover of shrubs and ground cover vegetation compared with unfenced control plots. Unexpectedly, camera traps revealed that swamp wallabies (W. bicolor) were 2 times more frequently detected than rusa deer, although deer tended to spend 6 times longer foraging than swamp wallabies when detected. Occupancy and activity of both vertebrate species did not vary between different habitat types, although there was a trend toward higher activity of swamp wallabies in the cleared revegetated area.